I gave this one a lot of thought. Paring down to one poster is an obscene request for any of us. I was originally going to go with One Million Years BC one-sheet, my first acquisition, but the more I thought about scarcity, importance, etc., I chose this one.
It's extremely hard to find and it has infamous
historical significance
thanks to that fargin' icehole,
Charles Manson...
The artwork (or at least the madcap characters across the lower portion of the poster) is by Frank Frazetta. I am unsure who did the close up art of Sharon Tate and Ferdy Mayne. I was considering asking Frazetta himself because there is very little info that I can find on this design. It doesn't look quite like his work -- though I could be wrong. Perhaps one of our more astute members might have some background to share.
Also, this is not my pic (I have my poster hermetically sealed in a fireproof tube at the mouth of a pneumatic tube that will send it rocketing out of the house in event of a fire). Mine has the day-glow orange logo. All in all it is a beautiful poster...